Conversion rates vary from business to business. I think a universal conversion rate of 5% is often mentioned - but not sure how useful that is, because as I say .. it varies from person to person.
over 1% for a sale for leads/signups, it depends on how much info is needed. For only email addresses, it should be around 50%. The more information needed, usually the lower the conversion rate will be.
As expected, numbers are flying around. A Conversion rate will differ dramatically from business to business. It's totally useless information to think of X% being good, in all honesty.